Stone disease is among the most painful and prevalent urological disorders. More than a million kidney stone cases are diagnosed each year with an estimated 10 percent of Americans destined to suffer from kidney stones at some point in their lives. The incidence of urolithiasis, or stone disease, is about 12% by age 70 for males and 5-6% for females in the United States. The debilitating effects of kidney stones are quite substantial, with patients incurring billions of dollars in treatment costs each year. Scientists do not always know what makes stones form. While certain foods may promote stones in susceptible people, researchers do not believe that eating specific items will cause stones in people who are not vulnerable. Yet factors such as a family or personal history of kidney stones and other urinary infections or diseases have a definite connection to this problem. Climate and water intake may also play a role in stone formation.
Normally, urine contains many dissolved substances. At times, some materials may become concentrated in the urine and form solid crystals. These crystals can lead to the development of stones when materials continue to build up around them. Stones formed in the kidney are called kidney stones. A ureteral stone is a kidney stone that has left the kidney and moved down into the ureter. The majority of stones contain calcium, with most of it being comprised of a material called calcium oxalate. Other types of stones include substances such as calcium phosphate, uric acid, cystine and struvite.
Stones form when there is an imbalance between certain chemical urinary components such as calcium, oxalate and phosphate. These chemical components either promote crystallization while others inhibit it. The most common stones contain calcium in combination with oxalate and phosphate. A less common type of stone is caused by infection in the urinary tract. This type of stone is called a struvite or infection stone. Much less common are the pure uric acid stones. Much rarer is the hereditary type of stones called cystine stones and even more rare are those linked to other hereditary disorders.
Although most stone formers do not have a medical condition that directly leads to their stone development, conditions do exist that place patients at high risk for stone formation. For example, stones can form because of obstruction to urinary passage like in prostate enlargement or stricture disease. Stone formation has also been linked to hyperarathyrodism, an endocrine disorder that results in more calcium in the urine. Susceptibility can also be raised among the people with rare hereditary disorders such as cystinuria (formation of cystine stones in the kidneys, ureter, and bladder or primary hyperoxaluria (excessive urinary excretion of oxalate).
Another condition that can cause stones to form is absorptive hypercalciuria, a surplus of calcium in the urine that occurs when the body absorbs too much from food. Another condition that results in a high level of calcium in the urine is resorptive hypercalciuria where the kidney leaks calcium into the urine. The high levels result in calcium oxalate or phosphate crystals forming in the kidneys or urinary tract. Similarly, hyperuricosuria, excess uric acid tied to gout or the excessive consumption of protein-rich products, may also trigger kidney stones. Consumption of calcium pills by a person who is at risk to form stones, certain diuretics or calcium-based antacids may increase the risk of forming stones by increasing the amount of calcium in the urine. Calcium oxalate stones may also form in people who have chronic inflammation of the bowel or who have had an intestinal bypass operation or ostomy. This is because of loss of more water from the body as well as absorption of oxalate from the intestine.
Once stones form in the urinary tract, they often grow with time and may change location within the kidney. Some stones may be washed out of the kidney by urine flow and end up trapped within the ureter or pass completely out of the urinary tract. Stones usually begin causing symptoms when they block the outflow of the urine from the kidney leading to the bladder because it causes the kidney to stretch. Usually, the symptoms are extreme pain which often begins suddenly as the stone moves in the urinary tract, causing irritation and blockage. Typically, a person feels a sharp, cramping pain in the back and in the side of the area of the kidney or in the lower abdomen, which may spread to the groin. Sometimes a person will complain of blood in the urine, nausea and vomiting. While stones may not produce any symptoms, they can be growing, causing irreversible damage to kidney function. More commonly, however, if a stone is not large enough to prompt major symptoms, it still can trigger a dull ache that is often confused with muscle or intestinal pain. If the stone is too large to pass easily, pain continues as the muscles in the wall of the tiny ureter try to squeeze the stone along into the bladder. One may feel the need to urinate more often or feel a burning sensation during urination. If the stone is close to the lower end of the ureter at the opening into the bladder, a person will frequently feel like they have not fully completed urination. If fever or chills accompany any of these symptoms, then there may be an infection.
Unfortunately, kidney stones are a recurrent disease. In general, the lifetime recurrence risk for a stone former is thought to approach 50%. Stone prevention, therefore, is essential, e.g., medication or diet should be changed to reduce recurrence risk.
Stone size, the number of stones and their location are perhaps the most important factors in deciding the appropriate treatment for a patient with kidney stones. The composition of a stone, if known, can also affect the choice of treatments. Options for surgical treatment of stones include Extracorporeal Shock Wave Lithotripsy (ESWL), Ureteroscopy (URS), Percutaneous nephrolithotomy (PNL), and Open Surgery. ESWL is the most frequently used procedure for eliminating kidney stones non-invasively by using sound waves. The technology is only effective if the kidney is functioning well and there is no blockage to the passage of stone fragments. Further, one ESWL session by itself may not free the ureter of all stone material, and either a repeat ESWL session or treatment with another approach may be necessary. ESWL is not the ideal treatment choice for all patients. Patients who are pregnant, obese, have obstruction past the stone, have abdominal aortic aneurysms, urinary tract infections or uncorrected bleeding disorders should not have ESWL. In addition, certain factors such as stone size, location and composition may require other alternatives for stone removal. Moreover, because of possible discomfort during the procedure, some anesthesia or some form of sedation is generally needed. While shock wave lithotripsy is considered safe and effective, it can still cause complications. Most patients have blood in their urine for a few days after treatment. Bruising and minor discomfort in the back or abdomen from the shock waves are also common. To reduce the risk of complications, urologists usually tell their patients to avoid aspirin and other drugs that affect blood clotting for several weeks before treatment. Another complication may occur if the shattered stone particles cause discomfort as they pass through the urinary tract. In some cases, the urologist will insert a small tube called a stent through the bladder into the ureter to help the fragments pass.
Therefore, there exists a need in the art for preventing or treating kidney and ureteral stones while reducing and alleviating symptoms and complications associated therewith.